Apparatus and method for production



March 3, 1964 K. M. OLIPHANT 3,123,564

APPARATUS AND METHOD FOR PRODUCTION OF METALLIC DEVELOPERS FOR ELECTROPHOTOGRAPHY AND METALLIC INKS AND PAINTS Filed March 16, 1961 INVENTOR. KEFI'H MERw-m OuPHAm EH Hi tys United States Patent APPARATUS AND h lETHOl); FUR PRODUCTIGN ()F METALLTC DEVELOPERS FOR ELECTRU- PHQTGGRAPHY AND METALLIC INKS AND PAINTS Keith Meredith Oliphant, Westhourne Park, SoutlrAus: tralia, Australia, assignor to Research Laboratories or Australia limited, Adelaide, South Australia, Australia Filed Mar. 16, 1961, Ser. No. 96,212 Claims priority, application Australia Mar. 17, 1960 11 Claims. (Cl. 252-621) This invention relates to the production of metallic developers for electrophotography and metallic inks and aints.

p Metallic inks and paints in the present state of the art consist of suspensions of relatively fine metal powders in vehicles which serve the dual purpose of carrying the powders and binding them firmly to the surface which is printed or painted. The advantage of metallic inks was considered to be the attractive rich appearance given to printed matter. Early metallic inks were based on coarse metallic powders suspended in a vehicle of natural resins and waxes dissolved in linseed or China-wood oil to which Canada balsam or Venice turpentine was frequently added to improve binding properties. The poor working properties of these inks led many printers to believe that all metallic inks were impractical. However, in recent years better metallic inks have been introduced which depend on the use of synthetic resins as the vehicle, such as modified phenolic resins. These newer vehicles were generally prepared by cooking the resin in a mixture of Chinawood and linseed oils at low heat so that the resin is in a labile form and not in complete solution. Various waxes, driers and reducers are then added to produce a vehicle of the desired viscosity, drying properties and stability.

Another and somewhat similar method of preparing metallic ink vehicles is to cook China-wood to the stage of incipient gelation and then chill immediately with raw linseed oil. The large fiocs of dispensed gel remain on the surface of the paper and hold the metallic pigment firmly, while the linseed oil penetrates into the paper and aids quick setting. Waxes, driers and mineral thinners are also required to control viscosity penetration and drymg.

Bronze powders are manufactured by rolling annealed bars of the various metals and alloys into thin sheets which are then shredded and stamped into fine flakes or particles by automatic reciprocating hammers in a stamping mill. The most modernmachines have vacuum sy-sterns by which the fine metal particles are drawn oil as they are formed. They are then sifted and the finer grades are air separated. This is followed by placing the powder and some stearic acid in a drum provided with polishing brushes and later stored for ageing.

The bronze powder and vehicle for preparing gold inks are generally supplied separately, to be mixed in the correct proportions by the printer just before use. This is considered necessary since the majority of the gold inks tarnish rapidly after the powder has been mixed with the vehicle. This is considered to be due to the acidity of the vehicle, the action of the driers on the powder or to the presence of traces of sulphur in the vehicle.

In mixing vehicle and bronze powder for printing on good grades of coated one side label, litho, glazed and gum papers, an approximate mixture is five parts of vehicle to four par-ts of powder by weight.

Aluminium powder in the form of a paste is made by placing small pieces of sheet aluminium or small aluminium pellets, in a steel ball mill together with a solvent like Varnolene and several percent of stearic acid and aluminium stearate. Grinding is continued until the prod- "ice not has reached the desired degree of fineness and brilliance, whereupon it is removed from the mill and after a suitable ageing period is ready for use. In the preparation of ready-mixed aluminium inks, the paste aluminium is generally mixed with about equal parts by weight of a viscous metallic ink vehicle.

It Will be seen that there is a wide variety of metal powders available for printing. It is also well known that for other applications of metal powders such as for example in powder metallurgy the manufacture of bearings from powdered metals, the coating of industrial objects with metal powders and also in cements, fairly coarse particles are desired such as 5 to 10 microns or greater. There are many methods of making metal powders, by mechanical grinding or by thermical reduction of metallic oxides or even metallic organic compounds. The principal difiiculty encountered in this Work is related to difficulty in producing fine particles less than 5 microns and in maintaining the particles in metallic form, preventing oxidation, tarnishing or other chemical change.

Accordingly, my invention is concerned with an improved method of producing powdered metals in a very finely divided form and maintaining these in an available form so as to exclude oxidation and tarnishing. Further my invention is designed to make these fine metal powders available in a suitable form for the production of printing ink, paint, coating compositions and developers for electrophotography.

The basic principle of my invention is three-fold: firstly, the metal powder is produced by a cutting action on a metal surface, not a hammering, abrading, rolling or distorting action; secondly, the powder is produced from a smooth surface; thirdly the operation is conducted so that the surface and cutting means is at all times immersed beneath the surface of an inert hydrocarbon liquid or inert gas so as to exclude chemical change of the particle surface as the new surfaces are revealed.

In one form of my invention the aim is to produce a metallic liquid developer. By the Way of example, a zinc plate is cleaned and immersed in a hydrocarbon liquid of high electrical resistivity, say 10 ohm centimeter, and low dielectric constant, say 3.

Abrasive cutting paper is rubbed on the zinc plate beneath the surface of the liquid until a desired concentration of powder is set up in the liquid. It is found that this suspension is stable and not subject to flocculation and can be used as a developer to produce fine grained electro-photographic images.

In another form of my invention, the aim is to produce a metallic ink. The surface of a bronze, silver or aluminium block is subjected to a cutting action for example beneath the surface of a liquid such as trichlorotrifluoroethane, known under the trademark Freon 113. This suspension when suificiently concentrated is mixed with a resin varnish for printing ink purposes.

In another form of my invention the metal plate of copper, silver, gold, platinum, zinc, steel or the like is subjected to a cutting action such as by the application of a diamond loaded dressing wheel, tip, or paper, under the surface of an inert liquid to which is added a resin which is soluble or partly soluble in the liquid. Such a combination of resin and liquid is for example an alkyd resin such as a long oil alkyd resin. The resin coats out on the metal particles as they are formed and provides means to fix the particles to the final surface, although the powder so produced is usually so line as to need no fixing agent. Another fixing material is for example bitumen in a hydrocarbon liquid.

The powders so produced are easily finer than 1 micron in size. The size depends on the quality of the surface which is cut and the fineness of the cutting compound used.

To enable the invention to be fully understood, embodiments will now be described with reference to the accompanying drawings in which:

FIG. 1 is a transverse section of one form of apparatus for eilecting the production of the metallic developers for electrophotography and metallic inks and paints, and

HG. 2 is a similar view but showing a modified form of the inventi n.

in the form shown in FIG. 1 a vessel 1 is provided with a top 2, an inlet 3 being associated with the top and an outlet 4 with the vessel.

The vessel 1 is adapted to contain a liquid 5 within which is submerged an abrasive ring 6 and a ring 7 of the material from which the powder is to be formed.

The ring 7 of the powder producing metal is fixed to a carrier 3 which is secured on the shaft 9 of a motor fixed to the vessel 1 so that as the motor shaft 9 revolves, the carrier 8 is similarly revolved to carry the ring 7 with it.

The abrasive ring 6 is similarly attached to a carrier 12 mounted on the shaft 13 of a motor 14 which is supported on a floating frame 15 which in turn is coupled through springs 16 to the top 2, the top 2 having an opening 17 through it to allow the floa ing frame 15 free movement in relation to the top 2, the opening being, however, sealed against egress of liquid by a resilient diaphragm 13 disposed between the edge of he opening 17 and an outer face on the floating frame 115.

A labyrinth packing l9 prevents the outnow of liquid 5 between the boss 2% of the carrier 12 and the floating frame 15, while a labyrinth packing 22 prevents leakage of the liquid 5 from the vessel 1 between the boss 23 of the carrier 3 and the vessel 1.

The motor 1% and the motor 14 is so driven that the abrasive rings 6 rotate in the opposite direction to the ing '7 of the powder producing material so that there is a polishing action or cutting action between the contiguous surfaces of the abrasive ring and the powder producing ring, this surface however being disposed beneath the level of the liquid 5 in the vessel 1 to ensure that the polls ng or grinding action on the powder producing ring '7 is carried out beneath the controlling liquid.

It will be realised of course that as the floating frame 15 carries the motor M which in turn carries the carrier 12, the weight can be so adjusts that the downward thrust on the carrier 12 gives the required cutting action between the abrasive ring 6 and the powder producing ring 7, the contacting surfaces of these two members being forced together by the pressure exerted due to the weight of the motor l4 and its associated carrying mechanism, but the pressure can be regulated by a correct selection of the springs 16.

A carrier 8 is provided with agitator blades 25 which keep the liquid stirred to ensure that as the powder is formed, it is maintained in a suspended condition in the liquid 5.

Liquid will of course be withdrawn from the vessel 1 as required when the necessary concentration of powder has been obtained, and if desired the process can be a continuous one under which there is a slow draw-off through the outlet 4 with a corresponding replacement of the liquid 5 through the inlet 3.

In the embodiment shown in PEG. 2 a vessel 3% supports a motor 31, a shaft 32 of which carries a carrier 33.

On the carrier are a series of boxes 34 having their outer ends open, each of these boxes 34 carrying in it a block 55 of the powder producing metal.

Attached to the vessel is a ring 36 of abrasive material, the position or" the ring 36 being such that the blocks of the powder producing metal will be thrown outwardly by centrifugal force into contact with this ring, so that as the shaft 32 or" the motor 31 is revolved, the carrier 33 will cause the boxes 34 which are secured thereon to move around and in turn causing the blocks 35 of the powder producing metal to rub against the abrasive 4 ring to produce the metal powder, the action being again beneath the liquid 37 in the vessel 30.

Vanes d4 fixed in the vessel 30 limit rotation of the liquid 37 in the vessel 39, these being necessary to ensure that the liquid will be maintained in a turbulent condition where it will at all times be available at the interface between the blocks 35 and the grinding or abrasive ing 36.

A lid 33 is held down on to the vessel 30 by clips 39, packing means ll) being interposed between the lid 38 and a flange 41 on the vessel 30.

Leakage of liquid 37 between the boss 42 of the carrier 33 and the vessel 3% is prevented by a labyrinth packing 43.

From the foregoing it willbe appreciated that the embodiment described with reference to FIG. 2 operates in a similar manner to the embodiment described with reference to H6. 1, in that liquid 37 is contained in a vessel 30 and the powder is produced by urging the blocks 35 of the powder producing metal against the abrasive ring 36 while revolving the carrier 33 to cause the blocks 35 to move in relation to the ring 36, the metal powder being thus produced under the surface of the liquid 37.

An outlet :5 is provided for the vessel 35 and liquid can be drawn off therethrough when the concentration of powder in the liquid is suficient, new liquid being added by removing the lid 38, although this process again could be continuous, by providing a continuous feed of liquid to the vessel 30 while drawing oil the liquid through the outlet 45 as required.

The following examples show how the invention may be applied:

(1) Liquid Developer 1 grm. abraded metal add raw linseed oil 1 grm.

(2) Printing Ink Formulation Solvent: White spirit.

Metal: Aluminium, aluminium bronze, tin bronze.

Grinding time at 3,000 revolutions per minute relative rotational speeds.

Minutes Aluminium 5 Aluminium bronze 12 Tin bronze 10 Resins added as binders for printing ink. For each gram of abraded metal add to solvent prior to grinding.

Grrns. Resin Scopol 4 IN 3 Stand oil 3 Scopol 4 IN is a long oil length vinyl toluene modified alkyd based on semi-drying/dehydrated castor oils.

Vinyl toluene content 10%. Oil length Acid value 3-6. Sp. gr. 20 C l.050+0.005.

Manufacturer Styrene Copolymers Ltd.

After grinding evaporate solvent to desired consistency for mechanical printing.

(3) Metallic Paint Solvent: White spirit.

Metal: Aluminium, bronze, aluminium bronze. Grinding time at 3,000 revolutions per minute.

Minutes Aluminium 5 Bronze Aluminium bronze 12 Binder resins added for paint. For each gram of abraded metal add (prior to grinding) Resin Rhodene L56/ 60 4 grams. Rhodene L56/60 is a rosin phenolic resin modified linseed wood oil alkyd (Polymer Corporation Interstate Pty. Ltd.).

Oil length 52%. Acid value 6-10. Sp. gr. 20 C 0.938O.948.

What I claim is:

1. For producing powdered metallic developers for electrophotography and metallic inks and paints, characterized by the presence of micron-sized metal powders, the method comprising: subjecting a substantially smooth planar surface of a solid plate of the metal, which is to produce the powder for said developers, to the cutting action of an abrasive surface rubbed continuously thereagainst beneath an inert liquid to produce said powder of the desired ultimate micron size in a single operation, said liquid containing a fixing agent for adhering the powders to an electrophotograpically sensitive surface, said fixing agent being present in said liquid during cutting and being soluble in said liquid.

2. The method according to claim 1 characterized in that the cutting is eifected by an abrasive member in contact with said metal with relative movement between same.

3. The method according to claim 1 characterized in that the inert fluid is a liquid which prevents oxidation of the powder as it is produced.

4. The method according to claim 1 characterized in that the inert fluid is a liquid which subsequently forms the carrier for the powder.

5. The method according to claim 1 wherein the metal is pro-polished to have a smooth surface which is maintained during cutting.

6. The method according to claim 1 wherein the fluid passes through the cutting zone during cutting to pick up the powder.

7. For producing metallic developers for electrophotography and metallic inks and paints, the method comprising subjecting the metal which is to produce the powder for the said developers to a cutting action beneath an inert liquid to produce said powder, said inert liquid being one which prevents oxidation of the powder as it is produced, said liquid subsequently forming the carrier for the powder, and a fixing agent for adhering the powders to a surface, present in the said liquid during cutting, said fixing agent being soluble in the said liquid.

8. For producing metallic developers for electrophotography and metallic inks and paints, apparatus comprising a vessel to contain liquid, a first carrier disposed in said vessel below the liquid level therein, said carrier being adapted to support a plate composed of the metal from which powder is to be produced, a second carrier adjacent said first carrier also carried by said vessel to be disposed beneath the level of the liquid therein, an abrasive member on said second carrier, the abrasive member being of such form as to produce micronsized powders when rubbed against the surface of said metal plate, means to urge a surface of said plate on to the said abrasive member, and means to move continuously at least one said carrier whereby the said abrasive member has relative motion to the surface of said plate presented thereto to cut the face of the metal beneath the said liquid.

9. For producing metallic developers for electrophotography and metallic inks and paints, apparatus comprising a vessel to contain liquid, a first carrier disposed in said vessel below the liquid level therein, said carrier being adapted to support a plate composed of the metal from which powder is to be produced, a second carrier adjacent said first carrier also carried by said vessel to be disposed beneath the level of the liquid therein, an abrasive member on said second carrier, the abrasive on said abrasive member being of such form as to produce micron-sized powders when rubbed against the surface of said metal plate, means to urge the said abrasive member on to the said metal, and means to rotate at least one said carrier whereby the said abrasive member has relative motion to the said metal to cut the face of the metal beneath the said liquid.

10. For producing metallic developers for electrophotography and metallic inks and paints, apparatus comprising a vessel to contain liquid, a motor below said vessel carried by said vessel having its shaft upwardly projecting in said vessel, a first carrier on said shaft disposed in said vessel below the liquid level therein, said carrier being adapted to support a plate composed of the metal from which powder is to be produced, a second motor above said vessel carried by said vessel coaxially with the first said motor but movable axially thereto having its shaft downwardly projecting into said vessel, a second carrier on said downwardly projecting shaft disposed beneath the level of the liquid in the vessel, an abrasive member on said second carrier, spring means between the upper said motor and the vessel to allow said abrasive member to be urged on to the said metal, said motors rotating oppositely whereby the said abrasive member has relative motion to the said metal to cut the face of the metal beneath the said liquid.

11. For producing metallic developers for electrophotography and metallic inks and paints, apparatus comprising a vessel to contain liquid, a motor below said vessel carried by said vessel having its shaft upwardly projecting in said vessel, a carrier on said shaft disposed in said vessel below the liquid level therein and adapted to support loosely, and movable outward by centrifugal force, a piece of metal from which powder is to be produced, an abrasive member in said vessel carried by said vessel coaxial with said vessel and in line with said metal, whereby the said metal has relative motion to the said abrasive member when the said carrier is rotated to cut the face of the metal beneath the said liquid.

References Cited in the file of this patent UNITED STATES PATENTS 666,409 Coleman Ian. 22, 1901 1,569,484 Hall Jan. 12, 1926 2,097,890 Myers Nov. 2, 1937 2,354,727 Wulff Aug. 1, 1944 2,552,676 Hill May 15, 1951 2,907,674 Metcalfe et a1. Oct. 6, 1959 OTHER REFERENCES Printing and Litho Inks, Wolfe, 4th ed., MacNair Dorland Co., 1949, pages 322-325. 

1. FOR PRODUCING POWDERED METALLIC DEVELOPERS FOR ELECTROPHOTOGRAPHY AND METALLIC INKS AND PAINTS, CHARACTERIZED BY THE PRESENCE OF MICRON-SIZED METAL POWDERS, THE METHOD COMPRISING: SUBJECTING A SUBSTANTIALLY SMOOTH PLANAR SURFACE OF A SOLID PLATE OF THE METAL, WHICH IS TO PRODUCE THE POWDER FOR SAID DEVELOPERS, TO THE CUTTING ACTION OF AN ABRASIVE SURFACE RUBBED CONTINUOUSLY THEREAGAINST BENEATH AN INERT LIQUID TO PRODUCE SAID POWDER OF THE DESIRED ULTIMATE MICRON SIZE IN A SINGLE OPERATION, SAID LIQUID CONTAINING A FIXING AGENT FOR ADHERING THE POWDERS TO AN ELECTROPHOTOGRAPHICALLY SENSITIVE SURFACE, SAID FIXING AGENT BEING PRESENT IN SAID LIQUID DURING CUTTING AND BEING SOLUBLE IN SAID LIQUID.
 8. FOR PRODUCING METALLIC DEVELOPERS FOR ELECTROPHOTOGRAPHY AND METALLIC INKS AND PAINTS, APPARATUS COMPRISING A VESSEL TO CONTAIN LIQUID, A FRIST CARRIER DISPOSED IN SAID VESSEL BELOW THE LIQUID LEVEL THEREIN, SAID CARRIER BEING ADAPTED TO SUPPORT A PLATE COMPOSED OF THE METAL FROM WHICH POWDER IS TO BE PRODUCED, A SECOND CARRIER ADJACENT SAID FIRST CARRIER ALSO CARRIED BY SAID VESSEL TO BE DISPOSED BENEATH THE LEVEL OF THE LIQUID THEREIN, AN ABRASIVE MEMBER ON SAID SECOND CARRIER, THE ABRASIVE MEMBER BEING OF SUCH FORM AS TO PRODUCE MICRONSIZED POWDERS WHEN RUBBED AGAINST THE SURFACE OF SAID METAL PLATE, MEANS TO URGE A SURFACE OF SAID PLATE ON TO THE SAID ABRASIVE MEMBER, AND MEANS TO MOVE CONTINUOUSLY AT LEAST ONE SAID CARRIER WHEREBY THE SAID ABRASIVE MEMBER HAS RELATIVE MOTION TO THE SURFACE OF SAID PLATE PRESENTED THERETO TO CUT THE FACE OF TEH METAL BENEATH THE SAID LIQUID. 